Rework dns_test_makezone()

The dns_test_makezone() helper function always assigns the created zone
to some view, which is not always necessary and complicates cleanup of
non-managed zones as they are required not to be assigned to any view.

Rework dns_test_makezone() in order to make it easier to use in unit
tests operating on non-managed zones.  Use dns_name_fromstring() instead
of dns_name_fromtext() to simplify code.  Do not use the CHECK() macro
and add comments to make code flow simpler to follow.  Use
dns_test_makeview() instead of dns_view_create().

Adjust existing unit tests using this function so that they still pass.

lib/dns/tests/dnstest.h

@@ -54,9 +54,25 @@ dns_test_end(void);
 isc_result_t
 dns_test_makeview(const char *name, dns_view_t **viewp);
 
+/*%
+ * Create a zone with origin 'name', return a pointer to the zone object in
+ * 'zonep'.
+ *
+ * If 'view' is set, the returned zone will be assigned to the passed view.
+ * 'createview' must be set to false when 'view' is non-NULL.
+ *
+ * If 'view' is not set and 'createview' is true, a new view is also created
+ * and the returned zone is assigned to it.  This imposes two requirements on
+ * the caller: 1) the returned zone has to be subsequently assigned to a zone
+ * manager, otherwise its cleanup will fail, 2) the created view has to be
+ * cleaned up by the caller.
+ *
+ * If 'view' is not set and 'createview' is false, the returned zone will not
+ * be assigned to any view.
+ */
 isc_result_t
 dns_test_makezone(const char *name, dns_zone_t **zonep, dns_view_t *view,
-				  isc_boolean_t keepview);
+		  isc_boolean_t createview);
 
 isc_result_t
 dns_test_setupzonemgr(void);